Rimma Finkel, Emese Kalnoki-Kis, and Morton Kasdan
DEFINITION
Since the beginning of the Industrial Revolution and the advent of industrial machinery, high-pressure injuries have been reported in the literature.
The force needed to break the skin is 100 pounds per square inch (psi). In general, high-pressure injuries are forced into the tissues at a pressure of 141 to 703 kg/cm2 (2000 to 12,000 psi)8 (FIG 1).
The substances typically injected include grease, paint, paint thinners, diesel fuel, oil, water, and cement. Cases involving molten metal,4 dry cleaning solvents,10 and veterinary vaccines6 also have been documented.
ANATOMY
The site of injection and pressure helps to determine the extent of injury.
Kaufman14,15 found that fingers that were injected with wax experienced tissue injury until a point of resistance was encountered. In the digits, the limiting factors to the extent of injury are the pulleys. He noted that the cruciate pulleys are pliable and thin, whereas the annular pulleys are rigid.
If the injection occurs at the level of the proximal or distal interphalangeal joints (PIP or DIP joints), the substance injected will dissect through the tendon sheath.14
The synovial sheaths of the index, long, and ring fingers extend to the metacarpophalangeal joint; the synovial sheaths of the thumb and little finger extend into the proximal palm at the radial and ulnar bursae.9
Any injections that occur over the middle segments of the fingers, away from the joints, will be diverted around the digit and spread laterally in the superficial tissues.14
Based on this information, the proximal spread of material can be predicted.
Injections into the palm, thenar, and hypothenar eminences are generally contained in those myofascial spaces and lead to less permanent impairment.18
The morbidity is determined by the volume, pressure, viscosity, resistance of the tissues, location of injection, anatomy of the compartment, and toxicity of the material injected.
PATHOGENESIS
High-pressure injuries are divided into three stages.
The acute stage occurs immediately.
The injection causes compression and spasm of the vessels, leading to compromised blood flow. This is manifested by white, mottled tissue; numbness; severe pain; or a combination of these findings.
Any initial paresthesias that occur are due to local compression or chemical irritation of the digital nerves.
During this stage, the site of injection is key in determining where the material has spread. Very high pressures can overcome tissue resistance.
The volume of material injected also determines the degree of tissue distention and impairment in blood flow.
In several studies by Gelberman,8 Schoo,25 and Hayes,12 patients with hands that had higher-volume injections and longer time to decompression had higher morbidity rates.
During the intermediate stage, a foreign body reaction induces oleogranuloma formation and fibrosis.
The inflammation that occurs is determined by the volume and type of substance.
The injection of paint solvent has a significantly higher morbidity due to its low viscosity, allowing diffusion through the soft tissues. Its corrosive effects cause severe tissue necrosis.9
Patients with grease injections have more chronic inflammatory reactions, leading to prolonged sequelae (foreign body granulomas).12,26
Schoo25 reported that amputation rates associated with various injection injuries were as follows: paint thinner, 80%; paint (soya alkyl base), 58%; automotive grease, 23%; and hydraulic fluid, 14%.
The late stage of injury occurs when the granulomas break open, resulting in draining sinuses and cutaneous lesions.
Chronic sinuses may degenerate into malignancies (squamous epithelioma).7,25
Secondary infections may occur in this stage; these may be due to Staphylococcus aureus, Streptococcus epidermidis, Pseudomonas spp., or a variety of polymicrobial flora.23,24
FIG 1 • An innocuous-appearing puncture of the volar radial surface of the right small finger. This may be the only visible point of injury in a high-pressure injection injury.
NATURAL HISTORY
Most patients with high-pressure injection injuries are young men. These injuries occur more commonly among manual laborers (FIG 2).
Previously it was thought that most of these injuries occurred to people who had been on the job for less than 6 months, but more recent studies show that the mean time on the job was 11 years.11,31
The nondominant hand (58%–76%)7,11 is injured more often than the dominant hand.
The index finger, thumb, palm, and small finger are affected in descending order.
Controversy continues as to what induces the inflammatory response in these injuries.
Some authors have suggested that the injury overwhelms the patient, leading to morbidity, whereas others believe that the injury induces a significant inflammatory response.
Most agree that surgery should be done within the first 3 hours after injury to decrease the morbidity.27,28
PATIENT HISTORY AND PHYSICAL FINDINGS
Important factors to discover include the patient’s hand dominance and occupation; the sequence of events post-injury; and the type of injector and pressure, as well as the substance injected.
Comorbidities, including vascular disease, diabetes, and smoking history, are relevant risk factors that influence healing and post-treatment function.18
If possible, the material safety data sheet (MSDS) for the substance injected should be obtained from the company.
Physical examination should include:
Determining the location of the puncture site to determine the spread of the injectate. It is not uncommon for the site of injury to be small and difficult to find.
Observing range of motion when the patient attempts to form a fist
Palpation of the digit, hand, and arm to help determine the extent of débridement that will be required
FIG 2 • Injury commonly occurs while attempting to clean a clogged high-pressure gun. Note that the guard has been removed.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographs of the hand and forearm are helpful in evaluating the extent of injury.
Although not all injected substances are radiopaque, air may be present in the compartments of the hand and forearm, which may help in determining how far the substance has traveled.20,23,30
It may be necessary to obtain radiographs of the arm and chest. Extension into the arm, chest wall, and mediastinum from injuries to the hand has been reported.29
Imaging studies also document pre-existing pathology.
DIFFERENTIAL DIAGNOSIS
Snake bite
Spider bite
Crush injury
Suppurative tenosynovitis
Black thorn tenosynovitis
Mycobacterium marina infection (chronic)
NONOPERATIVE MANAGEMENT
Most injuries require surgical débridement, and there are only few case reports of nonoperative management for such injuries.
Cases that are managed without surgery include air injection into the hand, which leads to subcutaneous emphysema that resolves within hours to days17 or, occasionally, water injection that is managed conservatively.16
SURGICAL MANAGEMENT
Early and aggressive decompression and débridement of all tissues is the cornerstone of treatment.
The time from injury to surgery is the major determinant of morbidity and prognosis in high-pressure injection injuries.27,28
Preoperative Planning
Radiographic studies should be reviewed.
Attention should be paid to radiopaque areas of the hand and forearm.
Air in the soft tissue should be evaluated.
The bones should be evaluated for any possible fractures or pre-existing lesions.
Any intravenous lines should be placed in the patient’s noninjured extremity, and manipulation of the injured extremity should be limited.
Positioning
The patient should be placed supine with the arm abducted.
The arm should not be exsanguinated with an Esmarch bandage, to avoid proximal spread of the injected material and further trauma to the tissues.
Regional anesthesia can be used to avoid general anesthesia, if necessary, but local blocks and injections should not be performed.
If the IV regional (Bier) block is selected, gravity exsanguination is performed without a compression wrap but with 4 minutes of elevation.
Approach
Two basic techniques are used to approach high-pressure injection injuries. Both are based on the idea of wide débridement, limited by scar formation over joint areas.
TECHNIQUES
BRUNER’S INCISIONS
The hand is prepped and exsanguinated by elevation.
For longitudinal exposure of the digits, it is important to avoid crossing the joint creases in a straight line. This is accomplished by creating Bruner zigzag incisions at the joint creases.
The digit is incised to avoid crossing the flexion creases so that no longitudinal incisions are made through the crease itself (TECH FIG 1A).
The injectate is removed, avoiding the neurovascular bundles located on the volar radial and volar ulnar surfaces of the digits.
The incision is continued across the palm, if necessary. The palmar incisions also are placed in such a manner as to avoid postoperative contracture of the crease (TECH FIG 1B).
If extension is necessary proximal to the wrist crease, the incision should be angled with the point toward the ulnar surface to avoid injury of the palmar sensory branch of the median nerve (TECH FIG 1C).
Extension onto the forearm may be longitudinal or in an S curve, if compartment decompression is necessary1–3 (TECH FIG 1D).
TECH FIG 1 • Bruner’s incision of the right index finger. A. The incision was made for adequate exposure to remove grease debris in the finger while avoiding crossing the joint creases. B. The incision is extended to the palm to allow for visualization of affected tissues and further débridement. C. Incision across the wrist crease. Crossing the crease is avoided by creating a Bruner’s incision or a curvilinear incision at the wrist crease. D.Longitudinal extension of the incision into the forearm. High-pressure injectate was pushed into the forearm tissues.
MIDAXIAL INCISIONS
Longitudinal midaxial incisions are made on the digit, radially and ulnarly.
These incisions are made dorsal to the neurovascular bundles (TECH FIG. 2).
If extension onto the palm is necessary, then it may be necessary to cross the web space, including the neurovascular bundles, but it must not be divided.
Incision across the palm continues as described for Bruner’s incision.3
TECH FIG 2 • Midaxial incision of the finger. This will sacrifice the dorsal branches of the neurovascular bundle, but the digital nerve and artery are protected in the volar tissues.
MODIFIED BRUNER’S INCISION
The digit is incised with a Bruner’s incision distal to the flexion crease, extending to the lateral aspect of the skin on the volar digital skin (TECH FIG 3A).
At the flexion crease, a transverse incision is made through the flexion crease, and the next interphalangeal incision is another oblique Bruner’s incision (TECH FIG 3B).
This is continued along the length of the digit onto the palm.
TECH FIG 3 • A. Modified Bruner’s incision with transverse extensions at the interphalangeal flexion creases allows for a widened visual field and more complete débridement. B. Modified Bruner’s incision at the metacarpophalangeal joint crease allows for visualization of the A1 pulley system, the neurovascular bundles, and the surrounding soft tissues.
POSTOPERATIVE CARE
The wound should be left open and packed, or very loosely closed. The hand should then be splinted in the “safe” position (FIG 3A,B).
Any additional débridement should be performed at 48-hour intervals, as necessary, until the wound can be primarily closed or covered (FIG 3C).
Less involved injuries often are allowed to heal by secondary intention, especially if critical structures are covered.
Occasionally, free tissue transfer may be necessary for coverage.5,22
Parenteral corticosteroids have been advocated to decrease the inflammatory response postoperatively.
The possibility of increasing the infection rate with corticosteroids does exist, although neither animal data nor human clinical findings show such an increase.
Animal studies have suggested that corticosteroids may be beneficial for patients sustaining injections of organic solvents.
No convincing human data have been published that show that corticosteroids are effective in limiting tissue loss, and they should be used cautiously.13,21
OUTCOMES
Outcomes of high-pressure injection injuries are based on the volume, pressure, viscosity, resistance of the tissues, location of injection, anatomy of the compartment, and toxicity of the material.
Morbidity includes cold intolerance, hypersensitivity, paresthesias, constant pain, impairment of the activities of daily living, infection, oleoma formation (FIG 4A), squamous degeneration,25 and amputation.
Amputation rates ranging from 14% to 88% have been reported in the literature.12,19,25
The highest amputation rates are associated with organic solvent injection into the fingers.13
In this subset of patients, the time to débridement also had a significant impact on the amputation rate.
If surgery occurs within 6 hours of injury, the amputation rate is 40%.
If the surgery is delayed for more than 6 hours, the amputation rate increases to 57%.
If débridement is delayed to more than 1 week after injury the amputation rate is 88%.13
Metacarpophalangeal range of motion decreases an average of 8.1%, proximal interphalangeal range of motion decreases 23.9%, and distal interphalangeal range of motion decreases by 29.7%.
FIG 3 • A. The “safe” position for postoperative splinting. The wrist is slightly extended, the metacarpophalangeal joints are fully flexed, and the digits are fully extended. B. Dynamic splinting of the hand in flexion to allow for early mobilization. C. Primary and split-thickness skin graft closure of a wound after final débridement.
Maximum grip strength diminishes by 12%, and pinch strength decreases by 35%.
Two-point discrimination increases by 49%31 (FIG 4B,C).
Permanent partial impairment of the injured hand depends on the mechanism of injury and the time to treatment.
The average impairment for injuries caused by spray guns is 15%, by pneumatic hoses less than 2%, and by hydraulic fluid 6%.30
If treatment is delayed more than 6 hours after injury, then the permanent impairment rate is approximately 17%; however, if treatment is obtained in under 6 hours, that rate is only 4%.30
Loss of work related to these injuries also varies, from 6 to 26 weeks, with about 92% of patients returning to their previous jobs.12
FIG 4 • A. Oleoma formation after débridement and closure of a digital high-pressure injection. The well-healed longitudinal incision on the volar surface of the digit is surrounded by yellow lesions, consistent with oleomas. B,C.Well-healed primary closures and split-thickness skin grafts of the volar and dorsal hand and forearm. There is full range of motion of the remaining digits after amputation of the index finger.
COMPLICATIONS
Infection
Cold intolerance
Hypersensitivity
Oleoma formation
Malignant degeneration
Decreased range of motion and function
Paresthesias
Diminished two-point discrimination
Amputation
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